View source for What happens if the human race presses the self-destruct button?

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Some extreme environmentalists like the fisherman, naturalist and essayist Pentti Linkola think that the world would be better off if the human race had never evolved. But can we think of a world with no intelligent humans? Science fiction authors and comic strip compilers imagine planets with life, often with cultures that are more advanced than ours. Nonetheless, their “Martians” tend to resemble us quite a lot, even if they have green coloured skin and antennas on their heads.

A well-known, although also controversial, author on paleontology and natural history, Stephen Jay Gould, ponders in his book ''Wonderful Life, The Burgess Shale and the Nature of History'' the likelihood of a species resembling the human being appearing if life were to start again from the beginning or even from some intermediary step. If human beings destroy their own species and much of the creation with hydrogen bombs, and all that would remain would be microbes, insects, scorpions and rats, would it be possible for a human-like creature to develop once again?


====The best will survive?====

After Charles Darwin’s celebrated interpretations on the origin of species (''On the Origin of Species'', 1859), many researchers thought that development is destined towards more competitive, more powerful and more intelligent species. They constructed family trees in which life starting in one species divides into several branches and continues upwards with more and more branches. On the top usually sat the mammals, particularly human beings. This easily leads to the concept that development towards more and more intelligent species is almost a natural law.

In 1909 a spectacular find was made in British Columbia in Canada, the Burgess fossils, a group of very weird animals that had been living in shallow water and which had been covered by a mud slide about 530 million years ago and entombed in shale. This makes it possible to study their anatomical structure even though they did not have hard parts such as a skeleton or a crust. Initially, the animals were classified to presently known phyla <ref>  In the classification of multicellular organisms the top class is kingdom (e.g. animal kingdom), the next is phylum (e.g. arthropoda, chordata) incorporating classes (e.g. insects or mammals); there may also be subclasses. </ref> and classes, because according to the dogma, everything had to be an early form of some presently known class. Only in the 1970s, was it shown that this cannot be true. In the Burgess fossils, one can find representatives of four classes of present-day arthropods, but in addition there are several arthropods that cannot be categorized into any presently known class.


====Diversity has decreased====

Life then used to be more diverse, not less diverse, than now. In a single shallow pond there were arthropods belonging to a number classes, actually a higher number than there are in all the oceans today.

What does this mean? Gould interprets this to mean that increasing diversity and the survival of the fittest does not explain the present animal kingdom. By studying the Burgess fossils, no obvious reason can be found to explain why those classes that survived did in fact survive. Those that became extinct did not lose out to others that were superior. Gould ends up hypothesizing that the forms of life were determined by the large extinctions that have occurred repeatedly. The fact that some creature disappeared could not be because it had developed in some inferior manner and was not competitive. Rather, survival was due to an incidental property that helped it to overcome a crisis, e.g. a long winter and prolonged darkness after a meteorite had blasted into the Earth. This property was not necessarily useful at all for survival under normal conditions.

Gould is asking himself the question, would human beings or even mammals have possibly conquered the world, if some other collection of the animals of the Burgess period had survived the crises instead of those which did survive. He considers that it is very unlikely. And if the meteorite had missed the Earth 65 million years ago, the appearance of human beings would probably be even less likely than the predominance of mammals. The mammals were living for one hundred million years side by side with the dinosaurs, but there is no sign that they could ever threaten their existence. Rather they were living as small and insignificant creatures in holes and niches on the edges of the world ruled by the mighty dinosaurs. But when a meteorite hit the Yukatan peninsula 65 million years ago, the great lizards did not survive the winter and darkness following the cloud of dust that shrouded the Earth blocking the sun. Then, and only then perhaps, the mammals had their chance.


====Survival during great extinctions was determined by chance====

Development of a species then is dead ends followed by more dead ends. For various reasons there have been mass extinctions where small numbers of apparently randomly selected living creatures survived. Since the numbers of species were greatly reduced, our surviving species are descendants of a few species only distantly related to each other. On the other hand, these classes divided into many directions of development. Therefore we have more than a million species of arthropods which belong to only four classes. The largest class is the insects which include more than a million species. All insects, however, are much more similar to each other than the Burgess fauna living in the one pond. Among the relatively few Burgess species, there were animals belonging to about 30 classes that did not resemble each other at all.

Even during the last few minutes of time in a geological sense there have been extinctions where a human-like development did not help. Both of our distant relatives ''Homo Neanderthalensis'' and the ''Homo erectus'' of Asia became extinct. Probably a minuscule population of ''Homo erectus'' survived in Africa, and our species, ''Homo sapiens'', descended from that branch. But why in Africa and not in Asia?


====Human being would not be reborn====

If human beings were to destroy themselves and a number of other species in the future, it would be very unlikely that another creature even remotely resembling the human being would ever be born. Similarly it is very unlikely that if there is life on some other planet, it would include a species in any way resembling human beings. Intelligence, perhaps, but it could as well reside in a multi-limbed, starlike animal such as a starfish rather than in a symmetrical creature with two legs and two hands.

Thus the human being can believe that there are two possibilities to explain his origin, either a very unlikely and fortunate series of multiple accidents, or a divine guidance in a very mysterious and elusive way. Neither of these possibilities contains the certainty that something similar would originate again.


'''''The best that human beings can do is to cherish this existing living world. This advice can be read already in the poetry of Genesis: “And the Lord God took the man, and put him into the garden of Eden to dress it and to keep it.”<ref> Gen. 2:15 </ref>'''''


'''Notes and references'''
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